This using a Microsoft Wedge Mobile keyboard (bluetooth) against a Nexus 7 2013, and not all things might work on all keyboards.
All tricks/tips is with keyboard connected/active.
With screen off on tablet, just press space bar or any key on the keyboard to wake the tablet.
Press Escape to exit from app, in some apps you exit the current song etc and returns to the main app itself.
On a regular screen (out an app), pressing any key will bring up Google Search.
If the keyboard got a Windows button (the Windows flag) you’ve got shortcuts as well.
E = E-mail, it will ask for default mail app the first time it’s pressed.
T = Hangouts
Y = Youtube
P = Google Music
A = Calculator
G = Gmail
L = Calendar
C = Contacts
B = Browser (Chrome)